BRIDGE 08 – FINAL REPORT ON REPAIRS plus REPORT ON BRIDGE 10 REPAIRS
Friday 4.2.22 - With just 11 working days (including weekends) left and barely half the original steel repairs completed, a sense of panic was starting to be felt!! During the course of the planned works, we had discovered numerous extra smallish steel repairs which we wanted to get done whilst we had steelwork contractors on site, which added to the pressure. Fortunately, the extra man who had started today, was able to take on these “extra” works whilst the original team got stuck into the original work remaining.
Week commencing Monday 7.2.22 - Over the weekend, 6 of the additional Ledger angles were fitted and fully profile welded into the webs of the two Outer Main Girders (OMG’s) and had a been given a coat of paint. (P. 1).
The last few new bolts were being fitted into Long girder 1 (L.G.1), and the last few rivets were coming out of L.G.2. The new plate on L.G.1 was now butted right up to the stub end of the original (P.2.)
and were then being welded to it (P.3).
Repairs to Jack-arch brickwork replacing damaged or missing bricks were also taking place (P.4). The bricks have to be held in place with wooden wedges whilst the mortar sets.
Meanwhile the last few rivets were drilled out (P.5) of L.G.2, and then the old plate was lowered onto two trolleys and drawn out onto the scaffold deck extension. Here it was to be used as a template to mark the new plate with holes.
At the same time work was taking place on the end of S.G.2 where it connects to the H-M OMG. The web plate had gone into holes (P. 6), and it was necessary to cut out the jack arch brickwork to find solid steel to weld to.
(P.7) shows the new plate welded in and the toothed Jack-arch brick which will have to be made good.
Next, the new plate for L.G.2 was lifted onto the loading part of the scaffold deck (P.8 & 9).
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| Lifting the new plate on to the scaffold deck. |
The old plate was then used as a template to mark the new hole positions and then they were drilled on site (p. 10).
The drilled plate was then rolled into place on the two trolleys (P. 11),
....ready for lifting using two Genie hoists (P. 12).
On S.G.2, adjacent plates alongside (P. 6), had reduced in thickness and were earmarked for more plates to be welded in (P.13) which shows in Blue some of the areas into which have plates welded.
Another small extra identified was the bearing plate where the LG2. sat on the U-S abutment padstone. This plate had been quite badly eaten away and so the worst part was cut out (P.14). Then a plate was welded in. All new steel was given one or two coats of good quality priming paint.
Monday 14.2.22, Tuesday 15.2.22 – the last bits of welding, painting and tidying up were completed and all of the equipment was lowered to the ground and carted off site. All steel work, construction work and painting activities was completed by the end of the day.
Wednesday 16.2.22 – A team of scaffolders arrived and what had taken 5 or 6 men - 5 days to install was removed in 2 days!! Main contractor Montel Civil Engineering were also removing all ancillary equipment – Heras fencing, and tidying up, but had also, in the meantime, they and their steelworkers had moved down to Bridge 10, (alongside Stanton yard) and had started work there. We had hoped might be possible, as there were important repairs needed to be done, but it depended on the availability of the various workers needed. It happened as described in the detailed report below.
Monday 21.2.22 – A team of propping contractors came to site and again, what had taken 5 or 6 men 5 days to install, was dismantled and packed ready for loading in one day!! By Tuesday it had all gone from site - Amazing.
The bridge was then ready to have the traffic lights removed. This was not part of the Br. 08 repair contract but is being arranged by others in GWSR. Issues like, burning off white lines and getting the road swept (mainly around the waiting signs where there is large a build-up of debris), have to be coordinated, but hopefully will be done, early next week.
Tuesday 22.2.22 & Wednesday 23.2.22 – Montel began removing the ballast plateau which had been constructed below the bridge to support the propping. There was about 120T of ballast to be removed and transported to the cess alongside Stanton yard, where it was to be stockpiled for use by GWSR in the future. The final action was to travel down the track with a small rubber tracked 360 and tidy up the edge of the track ballast where it had been disturbed by all of the vehicle movements. P-way collected the first of such loads was collected on Tuesday 22.2.22. The ballast transfer and tidying up the site was completed on Friday 25.2.22. This completed the original Br. 08 contracted work, - 3 days early!!!
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| View on completion, from the north. |
You would have thought that having spent over 3,000 manhours of hard work costing £ many thousands, working under the bridge, there would be something to see. However, as P. 15 & 16 show there is little obvious change. The sharp eyed amongst you might spot some areas of the steelwork where the paint is different colours. These are just good quality primer paints to delay corrosion. There will be further works to do in a year or two’s time, and, at that stage a full, lasting paint system will be applied as was done in 2007 – maybe 60% still looking good now.
BRIDGE 10 – STANTON ROAD – REPAIR WORKS
Bridge 10 carries the minor road into Stanton village and is right next to the GWSR Stanton yard. It was necessary to pass constantly under Br. 10 to get to Br. 08, and so there was not much that could be done on Br. 10 whilst the work at Br. O8 was still taking place. By the use of a mobile tower and a MEWP some could be done, especially above the track which is on the downside of the trackbed. (P. 1).
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| Down side abutment top |
The bridge is made up of 6 girders, which Jack-arch brickwork between them (P. 2).
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| Extra ledger angles on the low mileage side. |
As usual, damage to the outer verge areas of the road, when services were laid, has damaged the waterproofing and allowed water to get in. Added to that, as with Br. 08, the emissions from steam trains have damaged the steelwork above our running line (formerly the downside), and repairs done by Network Rail (or B.R.) (P.3).
The verges were dug out and some waterproofing was done, and the verge strips were then tarmacced, in October 2014, which helped.
The Jack-arch bricks are supported on Ledger angles (as Br. 08), and several areas of the horizontal leg holding the bricks up has gone thin and also become reduced in width. Removal of these for replacement is not possible as supporting the brickwork and leaving room to replace them is not physically possible. The only solution is to install supplementary angles below the existing and pack the gap with a suitable mortar. (P. 3).
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| Cutting out old tie bars |
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| View of tie bar work in bay 5. |
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| Cutting brickwork out to replace tie bars. |
The Jack-arches have an outwards thrust from the loads travelling over the bridge, and this thrust is contained by the use of 7/8” diam. steel tie bars. Several of these had rusted right through or were very thin and needed to be replaced. The tie bars are built into the brickwork at their ends, and this has to be broken out to free the tie bars. (P. 4, 5 & 6). The new ones are stainless steel so will last a very long time.
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| Extra ledger angles and patch plate. |
There were also several vertical steel web stiffeners which needed pieces welding in and a couple of other minor steel repairs which have been done too. (P. 7). We would like to do further works, but there simply isn’t enough time.
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| Brick displacement at the lower end of the wing wall. |
A problem common to most of our bridges is that the wing walls which retain the soil up to the ends of the abutments, fracture along a line roughly following the sloping line of the copings. (P. 8) and the brickwork slowly gets pushed forwards. This is because the ground around this area is a highly shrinkable clay. In the summer it dries out and large cracks open, allowing surface materials to be washed in. Then, in the winter, as it expands again, the soil washed into the cracks takes up more space and so the brickwork is “slowly “jacked” forwards. The soil behind the upper sections will have to be dug out, the walls taken down (salvaging the copings and bricks), then the wall tops can be re-built. Once the mortar has hardened a free draining stone will be placed to fill the gap and should stop future movement.
We will have to finish all work by p.m. tomorrow so that the track can be checked over, before any trains can run.
The site accommodation/welfare cabins will then be taken away over the following few days and so the more important repairs on these two bridges will have been dealt with.
Our thanks go to the main contractors, Montel Civil Engineering and their steelwork sub-contractors, Brunswick Ironworks for completing a very hard, awkward and not very exciting couple of contracts, and getting them finished, on time (Br. 08 actually 3 days early).
REPORT BY JOHN BALDERSTONE, STRUCTURES ENGINEER, GWSR. – 27.02.2022.
Editor's note: If you contributed to our successful £200.000 appeal, give yourself a pat on the back, you helped to achieve this! And thank you all.
